The primary goal is to examine the regulation of triacylglycerol metabolism in animal cells in order to gain a better understanding of the inter-relationships of triacylglycerol synthesis, uptake, and degradation on a molecular level. The proposed studies will contribute to current understanding of the development of atherosclerosis and of disorders such as obesity and diabetes which are associated with an increased incidence of coronary artery disease, hypertension and stroke. Triacylglycerol synthesis and degradation must be regulated during the formation of lipoproteins, the storage of intracellular triacylglycerol in adipocytes, and the accumulation of lipid droplets in hepatocytes and muscle cells. Abnormalities in regulation may play a role in the abnormal lipoprotein metabolism of diabetes and the genetic hyperlipidemias. Three approaches will be taken. These will be first, the development of improved highly sensitive and specific assays for each of the intracellular liver triacylglycerol lipases. Such assays are essential for systematic and detailed characterizations of the triacylglycerol lipases and their subcellular locations. The microsomal triacylglycerol lipase will be localized to the cytoplasmic or lumenal surface of the endoplasmic reticulum. The second approach will manipulate the nutritional or drug environment of animal cells in culture to test the responses of the glycerolipid synthetic and lipase activities. The third approach will select and study animal cell mutants which are defective in the regulation or in the enzyme activities in the pathways of triacylglycerol biosynthesis and degradation. These three approaches should clarify the roles of each of the intracellular lipases in the degradation of specific pools of triacylglycerol. They should also provide evidence for or against reciprocal regulation of triacylglycerol synthesis and degradation.